1. Field of the Invention
This specification relates a compressor, and particularly, to a compressor having a ball bearing installed at a thrust bearing surface between a cylinder block and a crank shaft, and a refrigerating machine having the same.
2. Background of the Invention
In general, a hermetic compressor is a compressor provided with a motor unit disposed in a hermetic container for generating a driving force, and a compression unit operated by receiving the driving force from the motor unit. The hermetic compressors may be categorized into a reciprocating type, a rotary type, a vane type and a scroll type according to the compression mechanism with respect to a refrigerant as a compressible fluid.
The reciprocating compressor is configured such that a crank shaft is coupled to a rotor of a motor unit, a connecting rod is coupled to the crankshaft of the motor unit and a piston is coupled to the connecting rod, so that the piston linearly reciprocates within a cylinder to thereby compress a refrigerant.
The reciprocating compressor is configured such that a shaft portion of a crank shaft is inserted into a cylinder block to be supported in a journal direction and simultaneously an eccentric mass portion is laid on the cylinder block to be supported in a thrust direction as well, thereby forming a journal bearing surface and a thrust bearing surface between the crank shaft and the cylinder block. Hence, how to reduce the frictional loss between the journal bearing surface and the thrust bearing surface as much as possible acts as an important factor on enhancing energy efficiency of the compressor.
To this end, an oil passage is formed at the crank shaft so that oil pumped from an oil feeder can evenly be supplied to each bearing surface via the oil passage.
However, the related art reciprocating compressor has a limitation on reducing a frictional loss because the cylinder block and the eccentric mass portion of the crank shaft, which define the thrust bearing surface, generate a surface-contact therebetween. Considering such limitation, an approach of installing a bearing, such as a ball bearing, which may generate a point-contact with the thrust bearing surface, has been introduced.
However, when the ball bearing is installed at the thrust bearing surface between the cylinder block and the crank shaft, a sliding contact may occur between the ball bearing and the cylinder block or crank shaft, which may cause more increase in the frictional loss.